Square pipe is a name for square pipe and rectangular pipe, that is, steel pipe with equal and unequal side lengths. It is made of rolled strip steel after process treatment. Generally, the strip steel is unpacked, leveled, crimped and welded to form a round pipe, then rolled into a square pipe, and then cut into the required length. Also known as square and rectangular cold-formed hollow section steel, referred to as square tube and rectangular tube, code names are F and J respectively.